Defects can be removed or lessened (especially on a flat surface) by a process called burnishing. A small round or cup-shaped metal tool is pushed into the surface to smooth out defects into the surface (such as a scratch) in order to make them less noticeable. Of course, doing this alters the level of theoriginal surface. Keys to detection are often a change of color, a depression, remaining scratches, and disruption of the metal flow. These are probably not visible in the image of the quarter.
I also received a little envelope that said "Pedigree" from Heritage Auctions for this coin - and I've discovered inside that this coin was apparently originally in a SEGS slab and graded... MS65.
Looks like someone had a big disappointment. Even with the assumption that a SEGS MS 65 would sell for a few grades lower, getting an AU Details would be a huge downgrade (and likely a big monetary loss for the seller).
Reminds me of the one time Larry Briggs showed up at our local show, with a massive array of SEGS-slabbed coins. I made some comment about "some of the nicest problem coins I've ever seen". He bristled, and said "what makes you think they're problem coins?" I said, "the word DETAILS printed right there on the SEGS label". He went back to his other conversation.
I just wanted to remark that I loved this thread! I wished we as a forum would have more "Guess the Sin," thread. I feel I am greatly deficient in identifying these sort of problems. Insider's threads help tremendously as well, but the theme of a sinned coin just seems fun. Thanks for posting.
Here was a long running thread that had plenty of details coins (started as a price guess thread and then went to guessing if it was details or not) https://www.cointalk.com/threads/the-details-discount-thread.301855/